Locks and keys are objects very familiar to people in daily life. Locks have various types, but always have paired keys for unlocking.
With the progress of sciences and technologies, locks and keys have long been out of mechanical correspondence. By using a car as an example, car unlocking may be implemented when a key is still a particular distance away from the car. The principle of car unlocking is that after a user presses an electronic key of the car, the electronic key transmits a radio frequency signal, a sensing apparatus in a car lock can identify the radio frequency signal corresponding thereto, and start an unlock operation.
In the related technology, the manner of unlocking by using an electronic key within a particular distance is widely used, but the security is not good. Now the event of opening a car by using a decoder for theft frequency occurs. Therefore, to improve the security of unlocking by using an electronic key within a particular distance becomes the problem demanding urgent solution.